Wireless network operators are strongly motivated to use resources in an efficient way, both in order to maximize their own profit and to provide services to customers at a reasonable price. Network optimization, that is, the placement and configuration of resources so as to maximize the area in which coverage is provided and the quality of service provided by that coverage, contributes greatly to the efficient use of resources. One way in which operators carry out network optimization is through drive testing, in which employees of an operator carry a device, such as user equipment (UE) with specialized measurement capabilities, through the service area of a network. The device is usually carried in an automobile, and as the employee drives to various points within the service area, the device collects data relating to the quality of the service that is being made available to it. Drive testing is obviously costly due to equipment and labor expenses, and particularly as the drive tests have to be repeated every time changes are made for the network configuration. Furthermore, the unnecessary use of automobiles contributes to air pollution and also presents some measure of personal danger to the employees performing the testing, because the possibility of traffic accidents is always present.
In order to minimize drive testing, operators are more and more turning to mechanisms that take advantage of the fact that customer devices are constantly receiving service in numerous locations throughout their service areas and that receiving information relating to the service experience of multiple devices can substitute for drive testing in many cases and can reduce or eliminate the need for drive testing. 3GPP release 10 includes a feature called “Minimization of Drive Tests” (MDT), which provides the ability for operators to gather information such as radio measurements which are associated with customer UEs and use this information to assist network optimization.
3GPP release 10 specifications relating to MDT for the LTE and UMTS radio access technologies may be found, for example, in 3GPP TS 32.422, TS 37.320, TS 36.331, and TS 25.331. There are two modes of MDT operation: Immediate MDT and Logged MDT. In Immediate MDT, UE-based information and eNodeB-based information are collected by the eNodeB while the UE is in the connected state and conveyed to a data storage server known as a trace collection entity (TCE). In Logged MDT, the UE stores UE-based information in a log while in the idle state, and the log is collected by the eNodeB and conveyed to a TCE at a later point in time when the UE is in the connected state. Examples of UE-based information are location information such as Global Navigation Satellite System (GNSS) coordinates, or downlink radio measurements such as Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ). An example of eNodeB-based information is uplink radio measurements such as Received Interference Power measurement.
The basic principles of MDT are expected to remain for 3GPP release 11. However, there is a work item to explore enhancements for Diverse Data Applications (eDDA) with the purpose of addressing potential issues that may arise from the prevalence of smart phones having ‘always-on’ applications running, such as email, RSS feeds, social network monitoring and the like. These applications require a constant or near constant connection with the network but will typically generate only intermittent traffic, generally small packets in the background without active usage of the terminal applications.
Relatedly, the UE can indicate if it wishes a power optimized configuration by sending a “preference for power optimized configuration” indication to the network. Such an indication informs the network that the UE prefers to be in a reduced power consumption state as compared to some default power consumption state.
There are in general two ways the network deals with the UE's ‘always-on’ applications. One way is for the network to release the UE's connection shortly after the always-on application's data transfer. This typically results in frequent state transitions between idle and connected states for the UE. If the UE is also configured for logged MDT there will be frequent retrieval of logged MDT data, and so the MDT reports will each have only a small number of samples due to the frequent state transitions which is not very efficient for the network's MDT purposes. The other way is for the network to keep the UE in connected state and configure the UE's discontinuous reception (DRX) to a very long interval, which allows the UE to sleep during the DRX period of the DRX cycle and thus conserve battery power. If the UE is also configured for immediate MDT there can be additional signalling which can negate the intended power savings from the long DRX period.